Verified answer

A past reality can exist because it has already occurred: it is a reality --

but that does not mean that it can be entered.

Consider yourself the focal point on an infinite highway, in your car,

and you are at the front of a million cars (or so ...) packed-in behind you.

You can go forward but, due to the density of the traffic behind you,

it is impossible to go back or even return to the tire tracks you left

only moments before .... or 100 miles ago.

This same density in 'past' provides a lock-and-key to prevent any tampering

with what has already occurred, and keeps everything rather intentionally

static in the here-and-now, and the future .... however and wherever you may find it.

Time Travel in "D" = YES! ----- Time Travel in "R" = Nope.

I don't think so. Like you said, past doesn't exist. Only memories of the past. There is no recorded past that we can go back to. I see life as a non rewindable and fast forwarding VHS tape.

Yes, but only in a forward direction.

We are in a time travel in +t direction. -t direction so far has eluded us.